MTB Complex

Non-cultivatable mycobacterium

• M leprae

4

Runyon Classification (1959) MOTT

Atypical mycobacterium• I Photochromogens → Yellow pigment formed after exposure to light when colonies grown in the dark and take more than 7 days• II scotochromogens → Yellow or orange pigment formed when colonies grown in the dark and take more than 7 days• III Nonphotochromogens → Colonies are non-pigmented regardless of whether grown in the dark or light and take more than 7 days• IV Rapid growers → colonis (pigmented or non- pigmented) that take less than 7 days

5

Rapid growers

Non Chromogens →ChromogensSee page 110

6

1

Number of tubercle bacilli required to establish infection

7

10

Average number of people that get infected by a single case of pulmonary TB

8

15

Number of years for which the incidence of TB has been progressively increasing in the UK

9

20

Time in hours for M. tuberculosis, a slow growing mycobacterium, to replicate

10

130

Hours of exposure to a case of infections pulmonary TB needed to be sure of contracting TB infection

MDR-TB (Multidrug Resistant TB) describes strains of tuberculosis that are resistant to at least the two main first-like TB drugs – isoniazid and rifampicin.

Is MDR – TB that is also resistant to three or more of the six classes of second-line drugs.

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MDR-TB

Resistance to anti-TB drugs in populations is a phenomenon that occurs primarily due to poorly managed TB care. Problems include incorrect drug prescribing practices by providers, poor quality drugs or erratic supply of drugs, and also patient non-adherence.

XDR-TB

1. First described in 20062. During 2000-20004, of 17, 690 TB isolates referred to international network of TB laboratories, 20% were MDR nd 2% were XDR3. In addition, population-based data on drug susceptibility of TB isolates were obtained from the United States (for 1993-2004), Latvia (for 2000-2002), and South Korea (for 2004), where 4%, 19% and 15% of MDR TB cases, respectively, were VDR

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Resistant TB →

A tuberculous cavity contains 107 to 109 bacilli. If mutations causing resistance to INH occurs in 1 in 106, and mutations causing RIF resistance occur in about 1 in 108, the probability of spontaneous MDR is 1 in 1014.